This invention relates to a method of manufacturing magnetic disk drives and, specifically, to the unique identification of magnetic disks before, during, and after the assembly of the disk drive.
A system to avoid accessing of defects or defective regions on a storage media is disclosed in U.S. Pat. No. 4,498,146 to Maria N. Martinez. The locations of defects on the disk, provided by the disk manufacturer are used to construct a list or table of addresses of defects on the storage media and is recorded on the disk data recording surface. Through conversion, the defect address list is used to produce real addresses of the defects on the disk recording surface. The resulting defect address table is loaded into the disk file controller and the addresses are used to prevent accessing the defective regions during disk drive operations. New defects may be added to the defect address table as detected.
A system for detection of contamination errors for optical disks is disclosed in U.S. Pat. No. 5,513,160 to Isao Satoh et al. The system first detects the defect errors on the disk and, at a later time, detects the total defect errors. The difference represents the contamination errors on an optical disk.
U.S. Pat. No. 5,075,804 issued to Deyring discloses a method for managing recording media defects. The identity and location of good or usable sectors of the recording tracks are maintained in an operating list stored in memory so that the disk drive microprocessor can avoid the use of bad sectors.
Presently, disk drives are comprised of disks that are not or have not been clearly individually identifiable. The disks have been individually tested and, if the disks pass the single disk test criteria, each single disk so tested and accepted is made available for assembly. Once assembled into the disk drive, these disks are retested for defects, and the locations of the defects are determined relative to the rotational datums of the disk drive. Thereafter, a defect table is assembled from the defect locations for each disk and stored on the media or in the memory of the disk controller. The duplicative testing of the disk is necessary both to prevent the use of a grossly defective disk and further to assemble the defect table of locations of the disk relative to disk drive established datums.
Currently, due to cost and inability to access and physically identify a unique disk surface once the disk drive is assembled, the surfaces of magnetic storage disks during the manufacturing process are not serially numbered or marked with any unique identification for later use in the assembled disk drive. Therefore, in the disk drive following assembly, the identity of a particular disk surface is not discernable.
Disk surfaces sometimes have laser scribed serialization; however, reading of the laser scribing requires a microprocessor and microprocessor associated image reading circuitry not found in a magnetic disk drive. Once assembled, however, the laser scribing is not readable in a magnetic disk drive.
As the current trend in magnetic disk drives of higher speed access rates continues, disk drives continue both to be reduced in size and also refined to store larger and larger amounts of data. Due to the very narrow width and close spacing of the data tracks on the disk, the affect of a surface defect in the recording media can render unusable, varying numbers of data tracks on a disk. A few surface defects affecting a nominal number of tracks may be tolerated; but, as the number of defects increases, the affected tracks and sectors soon start to severely limit the storage capacity of the disk.
The ability to identify and accurately account for or keep track of disk surfaces in assembled disk drives, particularly those drives in customer installations, is limited to identifying the disks by manufacturing lot or batch number. The manufacturing data for the disk drive may indicate the lot or batch numbers of the disks incorporated therein, but there is no certainty that the disk identity is reliable, particularly if there has been an overlap or changeover from lot to lot of disks incorporated into the disk drive assembly. Experience has shown that the lot or batch number associated in records with a particular disk drive is not accurate in many instances due to more than one lot or batch of disks being available on the manufacturing line at the same time, particularly whenever such lot or batch changeover occurs. Additionally, when more than one lot or batch number is used in a drive, presently there is no way to know which disk is from the lot being considered. Thus, in the event of a need to recall a lot or batch of disks due to a lot-wide defect, such as low coercivity of the magnetic coating or some other widespread type problem, a large number of disk drives may be needlessly recalled to insure that all the affected disks are identified.
It is very important that any disk drive placed in service not be displaced, removed from service, or disturbed imprudently because the affect can be extremely serious in terms of system down time. Being able to precisely identify individual disks already incorporated into an installed disk drive would permit avoiding use of a potentially defective disk in a drive, reduce the chance of data failure and an associated system crash and permit either the preservation of data or more orderly replacement of the disk drive at a time to minimize system disruption.
Serializing of a disk heretofore has been impractical at the single disk stage of manufacture inasmuch as the recording surface of the disk is not formatted at the single disk stage. Any widespread magnetic recording of readable data patterns thereon later interferes with reading and writing of data on the disk. Accordingly, the magnetic storing of a disk serial number and defect data on the disk has heretofore proved to be futile since the information either would not be reliably retrievable or the defect data would be effectively destroyed whenever the disk was formatted for servo control of the actuator following disk drive assembly and drive level testing.
Data storage disks typically have storage capacity on both sides of a disk. The disk surface includes a data storage region, an annular region near the periphery of the disk in which data is not stored, and an annular ring of substantial width which surrounds the central hole of the disk. As no effort is made to limit coating to only the data recordable portion of the surface, on each side of the disk, the magnetically coated and recordable surface of the annular storage portion of the disk extends between the central hole and the disk edge.
Part of the inner annular ring not used for data recording is used as a clamping region for engagement with inter-disk spacer rings resident on the disk drive hub. The balance of the inner annular ring and an outer ring adjacent the periphery of the disk may be used as a parking or landing zone or load/unload zone for the disk drive magnetic head whenever the drive is stopped, thereby preventing the head from contacting the recordable surface in the data storage zone of the disk surface which may result in disk surface and/or head damage.
The exposed portion of the inner ring and the outer ring are referred to as reserved areas. The manufacturing processes create recordable but otherwise unused surfaces in these reserved areas.
Heads for disk drives may be parked or loaded and unloaded either near the inner limits or the outer limits of the disk depending on the disk drive design. Thus, the magnetic read/write head is capable of being positioned at proper flying height over at least one of the reserved regions of a disk drive.
It is an object of the invention to readably serialize or otherwise readably uniquely identify each disk surface of a data storage disk drive at an individual disk level for identification in an assembled magnetic disk drive.
It is another object of the invention to serialize or otherwise uniquely identify the disk surfaces of a data storage drive in a manner that is readable in the assembled disk drive while not interfering with formatting, reading from or writing to such a disk surface.
It is a further object of the invention to improve the manufacturing and testing process of a disk drive and thereby enhance the reliability of the disk drive.
It is an additional object of the invention to enhance the accountability of the magnetic recording disks manufactured and tested for purposes of being able to identify specific disks in assembled disk drives and in customer systems.
It is a still further object of the invention to provide a method of manufacture for a data storage disk in such a manner as to permit the circumvention of a defective disk and the avoidance of a potentially disastrous incident and a possible loss of significant amounts of data.
It is yet another object to provide a disk drive with the ability to identify the disks incorporated therein by reading unique disk identifications from said disks.
A recordable magnetic disk for use in a magnetic disk drive is prepared using conventional disk fabrication, coating and curing techniques.
Thereafter, the disk is tested to determine defects in the magnetic disk recordable surface coating and/or ascertain the acceptability of the quality of the disk. If the defect level of the disk is excessive, the disk is scrapped and no record of the scrapped disk created or retained. Once a disk is determined to be acceptable, the disk is uniquely identified and a serial number or Disk Identification Number (DINUM) is recorded in one of the reserved areas of one side of the disk. The recording is made in a non-track specific manner, i.e., a magnetic pattern extending over a wide path in the selected reserved area. One example of such a recording pattern is a bar code type pattern which would extend across what might represent as many as 100 recording track widths. The recorded pattern not only provides uniquely identifying data but also a rotational orientation datum from which recording surface defects may be located.
Thereafter, the disk is selected and assembled with other parts and disks from varied lots or batches into a disk drive. The disk drive further is tested as a complete unit, and the defect location data previously determined in disk drive testing is retrieved from a computer data base using the DINUM or Disk Identification Number.
Formatting of the disk surfaces of the disk drive for servo control of the disk drive actuator is accomplished and supervised by a computerized routine which typically is not part of the control capability of the disk drive controller but rather the disk drive assembly testing controller. Thus, the formatting is accomplished after the single disk test.
During formatting of the disks, a pattern of recorded signals is recorded in each recording track of the typically 6,000 tracks on a 3xc2xd inch diameter disk. The signals are referred to as servo patterns. These servo pattern signals are used to insure that tracking or following of the data track by the disk drive read/write head is controlled and accurate. Without accurate tracking, data cannot be reliably recorded or read.
The formatting of the disk and recording of the servo patterns on the disk may be rotationally positioned to maximize usable recording secotrs. By judiciously positioning the servo patterns relative to previously detected surface defects, the number of sectors affected by the defects may be minimized and the recording capacity of the disk maximized.
The defect data base for a particular disk thereafter is stored in a defect table on the disk""s surface within the data storage area. The designations of areas identified by tracks and sectors which are usable also may be included in the defect table, as desired.
A greater understanding of the invention may be had from the drawings and the Detailed Description of the Invention to follow.